Method and apparatus for providing reliable multicast in a wireless communication system

ABSTRACT

A method and apparatus is described which provides reliable multicasting in a WLAN. The use of at least two distinct MAC multicast addresses are used to separate the first multicast frame transmissions from subsequent multicast frame re-transmissions. Thereby enabling legacy devices to ignore duplicate retransmitted multicast frames, because the duplicate frames are sent using a multicast address they do not listen to. Thus, the legacy devices are not confused with duplicated frames. In addition, new devices benefit from the retransmissions sent on the second multicast address and can re-order the frames before delivering to the applications or upper layers; thereby improving the QoS for the multicast.

CROSS-REFERENCE

This application claims the benefit of U.S. Provisional Application Ser.No. 60/865,617 filed Nov. 13, 2006, entitled “RELIABLE MULTICAST THROUGHMULTIPLE TRANSMISSIONS OF FRAME” the entirety of which is incorporatedherein by reference.

BACKGROUND

1. Field

The present disclosure relates generally to wireless communications andmore specifically to a method and apparatus for providing reliablemulticast in a Wireless Local Area Network (WLAN).

2. Background

WLANs have become popular and are used in many homes and businesses.WLANs can be found in places like coffee shops, Internet cafes,libraries, and public/private organizations. With the increase use ofWLANs, demand for broadcasting/multicasting has also steadily increased.Thus, a need exists for reliable multicasting.

Users want to be able to watch videos, receive newscasts, and otherlocal broadcast information. A commonly used communication protocol in aWLAN is the IEEE 802.11, which has the ability to multicast by utilizinga broadcast or multicast address within the MAC layer. However, the802.11 protocol does not support reliable multicasting, in that, themulticast frames are not acknowledged e.g. via acknowledgment (ACK)signaling and are not retransmitted.

Multicast frames are frames transmitted by an access point (AP) with thereceiver address set to one of a set of broadcast or multicastaddresses. A multicast address represents a group of recipients. The APmaintains only one multicast queue and associates a single sequencenumber space with all multicast and broadcast user data frames. Whenmulticast frames are transmitted with no ACK policy, their frame lossrates can be quite large. A loss rate of 10% is fairly typical. Framelosses can occur not only due to the signal-to-noise ratio (SNR)distribution depending on the location of the stations (STA) within theAP coverage area (e.g., the distance of the STA from the AP), but alsodue to overlapping transmissions, hidden terminal problems, etc.Although the coverage can be improved by lowering the data rate chosenfor the frame transmission, using a lower data rate results in the frametransmission occupying the medium for a longer duration, thus increasingthe likelihood of getting interfered by an overlapping transmission. Asa result, it is unlikely that the frame error rate of unacknowledgedtransmissions on an 802.11 WLAN can be reduced significantly. Thus, whenthe multicast frames are lost and the protocol does not retransmit, theservice becomes unacceptable to users.

In addition, a problem occurs in legacy devices if original multicast orbroadcast frames are retransmitted by the AP. A legacy device, forexample, may be one that uses any 802.11 protocol not modified accordingto the invention described here. The problem is that in a legacy devicethe MAC layer will not detect the duplicates causing the upper layers tobe confused by the duplicates. In other words, a legacy STA will passthe received multicasted frame up to the receiver stack to theapplication regardless if the legacy STA has received the same framepreviously. This will cause the STA to see out of order and duplicatepackets. This problem exists independent of what mechanism is introducedto cause an AP to transmit multiple copies multicast frames. Thus, thereis a need to provide support for legacy STAs as well as for newer STAsthat can benefit from retransmissions of the multicast or broadcastframes.

A proposed solution to these problems have been to allow fullacknowledgements. Allowing full acknowledgements of the multicast framesmay result in wasted bandwidth from acknowledgements transmitted by alldevices subscribed to the multicast stream and increased complexity ofdefining a protocol to obtain acknowledgments from all devices.

In order to overcome these problems, the present disclosure proposes asolution wherein the AP can make multiple retransmissions of framesassociated with a multicast stream without causing existing devices tosee out-of-order and duplicate frames, while providing improvedreliability for newer devices and working within the existing protocols.

Other benefits, features and advantages of the various aspects willbecome apparent from the following detailed description, figures andclaims. It should be understood, however, that the detailed descriptionand the specific examples, are given by way of illustration only, sincevarious changes and modifications within the spirit and scope of theinvention will become apparent to those skilled in the art from thisdetailed description.

SUMMARY

The following presents a simplified summary of the disclosed embodimentsin order to provide a basic understanding of such embodiments. Thissummary is not an extensive overview of all contemplated embodiments,and is intended to neither identify key or critical elements nordelineate the scope of such embodiments. A more detailed description ispresented later.

Methodologies and apparatuses are described that provide techniques forreliable multicasting in a wireless communication system.

According to an aspect of the disclosure, a method in which a multicastframe associated with a first multicast receiver address is transmitted,and a duplicate of the multicast frame associated with a secondmulticast receiver address is retransmitted. The second multicastreceiver address is different from the first multicast receiver address.

In another aspect of the disclosure, a computer-readable medium that hascode for causing a computer to transmit a multicast frame associatedwith a first multicast receiver address, and to retransmit a duplicateof the multicast frame with a second multicast receiver address that isdifferent from the first multicast receiver address. In addition, themulticast receiver addressing is done via the MAC layer.

In yet another aspect of the disclosure, an integrated circuit isconfigured to transmit a multicast frame associated with a firstmulticast receiver address, and to retransmit a duplicate of themulticast frame with a second multicast receiver address that isdifferent from the first multicast receiver address. Also, the twodifferent multicast frames have a portion of their headers in common.

Another aspect of the disclosure, is an apparatus with means fortransmitting a multicast frame associated with a first multicastreceiver address, and means for retransmitting a duplicate of themulticast frame with a second multicast receiver address that isdifferent from the first multicast receiver address.

In yet another aspect of the disclosure, a processor associated withsome memory is configured to transmit a multicast frame associated witha first multicast receiver address and to retransmit a duplicate of themulticast frame with a second multicast receiver address that isdifferent from the first multicast receiver. In addition, the multicastframe associated with the first multicast receiver address and theduplicate of the multicast frame associated with a second multicastreceiver address have a portion of their headers in common.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an embodiment of a wireless communication system;

FIG. 2 illustrates a flow chart demonstrating a process according to anaspect of the disclosure;

FIG. 3 illustrates a flow chart demonstrating a process according to anaspect of the disclosure that can utilize ACK, feedback, or Block ACKmessages;

FIG. 4 illustrates an embodiment in which the timing and addressing ofthe retransmissions is demonstrated;

FIG. 5 illustrates a simplified block diagram according to an aspect ofthe disclosure.

DETAILED DESCRIPTION

Various embodiments are now described with reference to the drawings,wherein like reference numerals are used to refer to like elementsthroughout. In the following description, for purposes of explanation,numerous specific details are set forth in order to provide a thoroughunderstanding of one or more aspects. It may be evident; however, thatsuch embodiment(s) may be practiced without these specific details. Inother instances, well-known structures and devices are shown in blockdiagram form in order to facilitate describing one or more embodiments.

As used in this application, the terms “component,” “module,” “system,”and the like are intended to refer to a computer-related entity, eitherhardware, firmware, a combination of hardware and software, software, orsoftware in execution. For example, a component may be, but is notlimited to being, a process running on a processor, an integratedcircuit, a processor, an object, an executable, a thread of execution, aprogram, and/or a computer. By way of illustration, both an applicationrunning on a computing device and the computing device can be acomponent. One or more components can reside within a process and/orthread of execution and a component may be localized on one computerand/or distributed between two or more computers. In addition, thesecomponents can execute from various computer readable media havingvarious data structures stored thereon. The components may communicateby way of local and/or remote processes such as in accordance with asignal having one or more data packets (e.g., data from one componentinteracting with another component in a local system, distributedsystem, and/or across a network such as the Internet with other systemsby way of the signal).

Furthermore, various embodiments are described herein in connection witha mobile device and/or an access point. A mobile device may refer to adevice providing voice and/or data connectivity to a user. A mobiledevice may be connected to a computing device such as a laptop computeror desktop computer, or it may be a self contained device such as apersonal digital assistant (PDA). A mobile device can also be called asystem, a subscriber unit, a wireless terminal, a subscriber station,mobile station, mobile, remote station, access point, remote terminal,access terminal (AT), user terminal, user agent, user device, or userequipment (UE). A mobile device may be a subscriber station (STA),wireless device, cellular telephone, PCS telephone, cordless telephone,a Session Initiation Protocol (SIP) phone, a wireless local loop (WLL)station, a personal digital assistant (PDA), a handheld device havingwireless connection capability, or other processing device connected toa wireless modem. An access point (e.g. base station) may refer to adevice in an access network that communicates over the air-interface,through one or more sectors, with mobile devices. The access point mayact as a router between the mobile device and the rest of the accessnetwork, which may include an Internet Protocol (IP) network, byconverting received air-interface frames to IP packets. The access pointalso coordinates management of attributes for the air interface.

Moreover, various aspects or features described herein may beimplemented as a method, apparatus, or article of manufacture usingstandard programming and/or engineering techniques. The term “article ofmanufacture” as used herein is intended to encompass a computer programaccessible from any computer-readable device, carrier, or media. Forexample, computer readable media can include but are not limited tomagnetic storage devices (e.g., hard disk, floppy disk, magnetic strips,etc.), optical disks (e.g., compact disk (CD), digital versatile disk(DVD), etc.), smart cards, and flash memory devices (e.g., card, stick,key drive, etc.).

Various embodiments will be presented in terms of systems that mayinclude a number of devices, components, modules, and the like. It is tobe understood and appreciated that the various systems may includeadditional devices, components, modules, etc. and/or may not include allof the devices, components, modules etc. discussed in connection withthe figures. A combination of these approaches may also be used.

The word “exemplary” is used herein to mean serving as an example,instance, or illustration. Any aspect described herein as “exemplary” isnot necessarily to be construed as preferred or advantageous over otheraspects.

Referring now to the drawings, FIG. 1 illustrates an embodiment of awireless communication system in which an aspect of the disclosure maybe implemented on. Illustrated is a system 100 that includes a WLANassociated with a wired local area network (LAN). Access point (AP) 102may be in communication with a newer protocol mobile device 104 and alegacy protocol device 110. Only two newer mobile devices 104 and onelegacy protocol mobile device 110 are illustrated for simplicity, butmany devices may be in communication with the access point 102. Theaccess point 102 may also be referred to as a base station (BS), a NodeB, a sector, or other similar terminology. Access point 102 may beconnected to an Ethernet hub or switch 112 for a LAN. Ethernet hub 112may be connected to one or more electronic devices 114 which may includepersonal computers, peripheral devices (e.g., facsimile machines,copiers, printers, scanners, etc.), servers, and the like. Ethernet hub112 may be connected to a router 106 that transmits data packets to amodem 108. Modem 108 may transmit data packets to a wide area network(WAN) 120, such as the Internet. System 100 illustrates a single, simplenetwork configuration. Many additional configurations of system 100including alternative electronic devices may be implemented. Althoughsystem 100 has been illustrated and describe with reference to a WLAN,system 100 may also utilize other technologies including WWAN and/orWPAN either separately or concurrently.

The newer mobile device 104 may utilize newer protocols such as thosedescribed in this invention. Throughout this disclosure, a “non-legacy”mobile or device is considered to be a device that utilizes a newerprotocol. The legacy protocol mobile device 110 may utilize a legacyprotocol, for example, IEEE 802.11 including any of the addendadescribed in 802.11a, 802.11b, 802.11g, 802.11v, 802.11n, or 802.11e.Throughout this disclosure, a legacy mobile device may also be called alegacy mobile, device, or station. Access point 102 may be broadcastingor multicasting information to the newer and legacy devices.

FIG. 2 illustrates a flow chart demonstrating a process 200 according toan aspect of the disclosure. In this exemplary process 200, an accesspoint 102 (such as described in FIG. 1) is multicasting to a newer 104and a legacy 110 device. Starting at step 202, a multicast stream istransmitted by an access point using an assigned multicast address. The802.11 standard allows multicast and broadcast addressing in the MAClayer. For example, the 802.11 MAC layer has four address fields definedin the MAC frame format. The fields are used to indicate: the sourceaddress, the destination address, the transmitting station address, andthe receiving station address. The destination address may be used toaddress an individual or a group. In addition to the address fields, the802.11 protocol has a sequence field that may be used to requestretransmission of a unique frame or to organize the original andretransmitted frames to keep them in order. Since broadcast andmulticast frames are not retransmitted in the existing 802.11 protocols,legacy devices ignore the sequence field in broadcast and multicastframes. Referring to a data frame for the 802.11, address one (1)typically contains the destination address which may be used for anindividual or group. Address two (2) typically identifies thetransmitting station. Thus, using the 802.11 example, at step 202, theaccess point may send out a multicast address in address one (1) of thedata frame. A non-legacy and a legacy device may have subscribed to thatmulticast group and therefore will receive the frame. At step 204, thelegacy device receives the multicast frame. In conjunction, at step 206,the non-legacy mobile device receives the multicast frame. Currently in802.11, multicast frames are not acknowledged (ACKed) or retransmitted.An aspect of the disclosure is to retransmit the multicast frames sothat the devices may benefit from the retransmission in the event of alost frame. Degradation of the quality of service (QoS) happens when theframe loss rate is not zero. If the frame loss rate is high enough, themulticast service may be inoperable. By retransmitting multicast framesthe problems associated with frame loss rates are solved. However, ifthe access point retransmits the frames using the same multicastaddress, then a problem occurs within legacy devices. The legacyprotocols do not support frame sequencing and duplicate detection formulticast and broadcast frames. As a result, when the legacy devicereceives a duplicate retransmitted multicast or broadcast frame it willpass the frame up to the application or upper layers as if it was a neworiginal frame being received. This causes confusion at the applicationsrunning on the legacy device and unsatisfactory service to the end user.Thus, an aspect of the disclosure is to provide a second multicastaddress that is different from the first multicast address which willenable the legacy device to discard the retransmitted duplicate framesas belonging to a multicast stream to which it is not subscribed therebysolving the problem of the legacy devices being confused by duplicateretransmitted frames. At step 208, the access point retransmits aduplicate frame at the next interval using a second multicast address.The second multicast address is different from the first address. In thecase of a broadcast stream which has a unique broadcast address, theaccess point may use a specific multicast address assigned for theduplicate transmissions of broadcast frames. At step 210, the legacydevice does not recognize the second multicast address as one to whichit is subscribed and discards the duplicate retransmitted frame and theprocess ends for the legacy device. In parallel, with step 210, at step212, the non-legacy device receives the retransmitted frames and is ableto distinguish the duplicate frame from the original as a retransmissionof the original and belonging to the same multicast stream. The processmay end for the non-legacy device at this point, or in an optionalaspect of the disclosure proceed to step 214. At step 214, the accesspoint may retransmit the duplicate multicast frame again. The non-legacydevice may use the sequence number of the retransmitted frame todistinguish when more than one instance of a retransmitted frame isreceived for a given second multicast address. In an optional aspect ofthe disclosure, the access point may use a third multicast address oragain use the second multicast address for the retransmissions. Anotheroptional aspect of the disclosure is that the access point may set athreshold or limit for the total number of times the frames could beretransmitted. For example, the access point may set the threshold tofour (4), therefore the steps 210, 212 and 214 may be repeated until thethreshold of four (4) is met. Another optional aspect of the disclosureis for at least one of the devices from the multicast group to send afeedback message back to the access point thereby assisting the accesspoint in determining the number of retransmissions required.

FIG. 3 illustrates a flow chart demonstrating a process 300 according toan aspect of the disclosure that can utilize ACK, feedback, or Block ACKmessages. At step 302, an access point transmits a multicast frame usingan assigned multicast address. The multicast frame is received by agroup of devices at step 306. At step 316, in an optional aspect of thedisclosure, at least one of the newer devices in the multicast groupsends an ACK or feedback message back to the access point indicatingthat the transmitted multicast frame is successfully received. Anotheroptional aspect is that a subset of the multicast group may also send aBlock ACK message back to the access point indicating their status ofthe transmitted multicast frame, in conjunction, the process may proceedto step 308. The ability to send ACKs or feedback of the multicasttransmissions may be statically or dynamically assigned. For example, amobile device may be designated to send ACKs depending on its locationwithin the WLAN. Over time, the AP uses the statistics of received ACKsand lost frames to adapt the number of retransmissions to use for themulticast stream.

The subset group may be non-legacy or legacy devices. In large multicastgroups it is desirable to collect statistics from only a subset of thestations in order to reduce overhead and avoid wasting system resources.By allowing only a subset of the devise to send feedback this may allowpremium services for selected devices. For example, devices that may paymore for a higher quality of service may be a device that is allowed tosend feedback thereby influencing the retransmissions of the AP.

The ability to send feedback may be statically or dynamically assigned.For example, a mobile device may be configured to send an ACK, feedback,or Block ACK depending on its location within the WLAN. Further the APmay optionally schedule the selected stations in order to collect theirfeedback with the Power Save Multi Poll (PSMP) frame defined in 802.11n.The PSMP frame may be used to announce the multicast transmission andthen reserve specific medium time for selected stations to transmittheir feedback, which may be a Block ACK. After the feedback is sent atstep 316, the process may proceed back to step 302 where the accesspoint transmits the frame using the original assigned multicast address,the process may end, or proceed to step 308. At step 308, the multicastframe is retransmitted using a second or new multicast address. Theprocess proceeds to step 312 where the retransmit (duplicate) multicastframe is received by the devices. The process may end or optionallyproceed back to step 308. Combinations of various optional aspects arepossible. For example, the aspect of using a second multicast frameaddress may be combined with the optional aspect to allow a subset ofdevices to send Block ACKs. The optional aspect of using a separatemulticast address per retransmitted frame may also be combined.Furthermore, determining when to send the retransmitted frames isdetermined based on the protocol, system, and other network factors.Using the 802.11 example, the retransmitted frames may be retransmittedon the next beacon interval. A beacon interval represents the number oftime units between target beacon transmission times. However, theretransmitted frames may be retransmitted on the next or upcomingframes, superframes, time slots, etc. Over time, the AP can use thestatistics of successful and lost frames fed back by the subset ofstations to adapt the number of retransmissions to use for the multicaststream.

FIG. 4 illustrates an embodiment in which the timing and addressing 400of the retransmissions is demonstrated. The processes 200 and 300described above may use the timing and addressing 400 as illustrated inFIG. 4. For simplicity, the time line is divided into three (3) beaconintervals: beacon interval one (1) 404, beacon interval two (2) 406, andbeacon interval three (3) 408. Beacons 402 are shown to be transmittedwithin the beacon intervals. Referring back to the process 200 in FIG.2, at step 202 an access point transmits a multicast frame using anassigned multicast address. In regards to FIG. 4, this multicast addressis called K. In the case of broadcast frames, K may represent the uniquebroadcast address. Frames (N) 410, (N+1) 412, and (N+2) 414 aretransmitted by the access point using multicast address K during beaconinterval one (1) 404. Proceeding to steps 204 and 206, the multicastframes are received by both legacy and non-legacy devices. Then at step208, the access point retransmits a duplicate frame. In reference toFIG. 4, this duplicate retransmitted frame is given a new multicastaddress called K+1. For the case of broadcast frames, instead, aspecific multicast address K* is assigned for this purpose. Forillustration, the retransmissions are shown to be transmitted in asubsequent beacon interval. There is a tradeoff between latencyrequirements of multicast and broadcast streams, and power management atdevices subscribed to multicast and broadcast streams. Broadcast andmulticast transmissions for legacy devices always follow the beacon toallow power-save devices to sleep during the inter-beacon period. Fornewer devices this restriction may not apply and retransmissions ofmulticast and broadcast frames may be scheduled within the inter-beaconperiod, if desired. Depending on the latency requirement of themulticast stream, the retransmissions with multicast address K+1 may betransmitted immediately after the initial transmission with multicastaddress K. Power-save considerations may still prefer broadcast andmulticast frame transmissions to follow beacons. Thus, during beaconinterval two (2) 406, frame (N+3) 416 is transmitted using the multicastaddress K and duplicate frames (N) 410 r, (N+1) 412 r, and (N+2) 414 rare retransmitted using the second or new multicast address K+1. Theprocess continues to transmit the original multicast frames using thefirst multicast address K and retransmitted frames using the second ornew address K+1. For this example, during beacon interval three (3) 408,the frames (N+4) 418 and (N+5) 420 are transmitted using the multicastaddress K. While frame (N+3) 416 r is retransmitted using the second ornew multicast address K+1. Many different timing and addresscombinations may be devised. For example, during beacon interval three(3) 408 a third or new multicast address K+2 could be used to retransmitthe duplicate frames. The retransmitted frames may be retransmitted onthe next beacon or time interval or on an upcoming beacon or timeinterval. The frames may be transmitted sequentially in time, atintervals, or randomly. Furthermore, different amounts and combinationsof original and retransmitted frames may be sent during the beaconintervals. Also, the retransmitted frames may continue to beretransmitted until a threshold is reached. Referring to the optionalstep 316 in FIG. 3 in which at least one of the devices may send afeedback or a subset of the devices sends a block ACK back to the accesspoint, the frames could be retransmitted within a particular beaconinterval or with predetermined timing pattern. The schedulingillustrated in FIG. 4 is for exemplary purposes to explain the conceptof the aspect of the disclosure with regards to how a WLAN may schedulethe retransmissions using the different multicast addresses. Differentscheduling combinations may be devised, and may be dependent on factorssuch as the protocol being used, the system, loading, etc. Thus, thisillustration is not intended to be limited to the example illustratedherein. Access point 102 as described above may be an access point 500as illustrated in FIG. 5.

FIG. 5 illustrates a simplified block diagram according to an aspect ofthe disclosure. Access point 500 comprises an antenna 510, a transceivercomponent 508, a memory component 512, a bus 506, and a processor 504.The access point 500 may include a WWAN (e.g., Code-Division MultipleAccess (CDMA), Wideband Code-Vision Multiple Access (WCDMA), orOrthogonal Frequency Division Multiple Access (OFDMA)), WLAN (e.g., IEEE802.11) and/or related technologies.

In an aspect, the processor 504 may provide WLAN functionality and becapable of communication with the transceiver 508 and the memory 512through the bus 506 or other structures or devices. The processor 504may utilize the processes described above in FIGS. 2 and 3. For example,the processor 504 may be configured to transmit a multicast frameassociated with a first multicast receiver address to legacy andnon-legacy devices within the WLAN, and be configured to retransmit aduplicate of the multicast frame using a second multicast receiveraddress different from the first multicast receiver address. It shouldbe understood that communication means other than busses may be utilizewith the disclosed aspects. Transceiver 508 is coupled to one or moreantennas 510 to allow transmission and/or reception by the access point500. Processor 504 may generate voice data provided to transceiver 508for communication. In an aspect, the processor 504 may be included in aprocessor. In another aspect, the processor 504 may be provided bydistinct integrated circuits. In another aspect, the processor 504 maycommunicate and work in corporation with a processor. In a furtheraspect, the processor 504 may be provided by one or more integratedcircuits, processors, ASICs, FPGAs, combinations thereof, or the likeincluding functionality.

Those skilled in the art would further appreciate that the variousillustrative logical blocks, modules, and steps described in connectionwith the aspects disclosed herein may be implemented as hardware,software, firmware, or any combination thereof and hardwareimplementation may be digital, analog or both. To clearly illustratethis interchangeability of hardware and software, various illustrativecomponents, blocks, modules, and steps have been described abovegenerally in terms of their functionality. Whether such functionality isimplemented as hardware or software depends upon the particularapplication and design constraints imposed on the overall system.Skilled artisans may implement the described functionality in varyingways for each particular application, but such implementation decisionsshould not be interpreted as causing a departure from the scope of thisdisclosure.

The various illustrative logical blocks, and modules described inconnection with the aspects disclosed herein may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device,discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, anintegrated circuit, one or more microprocessors in conjunction with aDSP core, or any other such configuration.

An exemplary storage medium is coupled to the processor such theprocessor could read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor. The processor and the storage medium may reside in anASIC. The ASIC may reside in a user terminal. In the alternative, theprocessor and the storage medium may reside as discrete components in auser terminal.

The steps or functions of a method or algorithm described in connectionwith the aspects disclosed herein may be embodied directly in hardware,in software executed by a processor, or in a combination of the two. Thesteps or functions could be interchanged without departing from thescope of the aspects.

If the steps or functions are implemented in software, the steps orfunctions may be stored on or transmitted over as one or moreinstructions of code on a computer-readable medium. Computer-readablemedia includes both computer storage media and communication mediaincluding any media that facilitates transfer of a computer program fromone place to another. A storage media may be any available media thatcould be assessed by a general purpose or special purpose computer. Byway of example, and not limitation, such computer-readable media couldcomprise RAM, flash memory, ROM, EPROM, EEPROM, registers, hard disk, aremovable disk, a CD-ROM, optical disk storage, magnetic disk storage,magnetic storage devices, or any other medium that can be used to carryor store desired program code means in the form of instructions or datastructures and that can be accessed by a general-purpose orspecial-purpose computer, or a general-purpose or special-purposeprocessor. Also, any connection is properly termed a computer-readablemedium. For example, if the software is transmitted from a website,server, or other remote source, using a coaxial cable, fiber opticcable, twisted pair, digital subscriber line (DSL), or wirelesstechnologies such as infrared, radio, and microwave, then the coaxialcable, fiber optic cable, twisted pair, digital subscriber line (DSL),or wireless technologies such as infrared, radio, and microwave areincluded in the definition of medium. Disk and disc, as used herein,includes compact disc (CD), laser disc, optical disc, digital versatiledisc (DVD), floppy disk and blu-ray disc where disks usually reproducedata magnetically, while discs reproduce data optically. A computerprogram product would also indicate materials to package the CD orsoftware medium therein. Combinations of the above should also beincluded within the scope of computer-readable media.

The previous description of the certain aspects is provided to enableany person skilled in the art to make or use the invention. Variousmodifications to these aspects will be readily apparent to those skilledin the art, and the generic principles defined herein may be applied toother aspects without departing from the scope of this disclosure. Thus,this disclosure is not intended to be limited to the aspects shownherein but is to be accorded the widest scope consistent with theprinciples and novel features disclosed herein.

1. A method for reliable multicasting in a wireless communicationsystem, comprising: transmitting a multicast frame associated with afirst multicast receiver address; and retransmitting a duplicate of themulticast frame, the duplicate being associated with a second multicastreceiver address different from the first multicast receiver address. 2.The method of claim 1, further comprising: receiving a feedbackassociated with the multicast frame from at least one of a multicastgroup, wherein the received feedback determines the number of duplicateretransmissions of the multicast frame.
 3. The method of claim 2,wherein the feedback is collected from one device in the multicastgroup.
 4. The method of claim 2, wherein the feedback is collected froma subset of devices in the multicast group.
 5. The method of claim 2,wherein the feedback is an ACK message.
 6. The method of claim 2,wherein the feedback is a block ACK message.
 7. The method of claim 2,further comprising: scheduling the feedback based upon Power Save MultiPoll (PSMP).
 8. The method of claim 1, further comprising: signaling thesecond multicast receiver address to at least one device of a multicastgroup.
 9. The method of claim 1, wherein the multicast frame associatedwith the first multicast receiver address and the duplicate of themulticast frame associated with a second multicast receiver address havea portion of their headers in common.
 10. The method of claim 9, whereinthe portion of their headers in common is a sequence number.
 11. Themethod of claim 9, further comprising: receiving the multicast frame andthe duplicate frame on a non-legacy device, wherein the non-legacydevice detects the duplicate frame based upon the frame headers.
 12. Themethod of claim 9, further comprising: receiving the multicast frame andthe duplicate frame on a legacy device, wherein the legacy devicediscards the duplicate frame based upon the frame headers.
 13. Themethod of claim 1, further comprising: setting a threshold for a numberof retransmissions for the multicast frame, wherein the retransmittingthe duplicate of the multicast frame repeats until the threshold is met.14. The method of claim 1, further comprising: retransmitting theduplicate frames on an upcoming beacon interval; and using a uniquemulticast address for the retransmissions in each beacon interval. 15.The method of claim 12, wherein the legacy device utilizes a protocolselected from the group consisting of: IEEE 802.11, IEEE 802.11a, IEEE802.11b, IEEE 802.11g, IEEE 802.11e, IEEE 802.11v, and IEEE 802.11n. 16.The method of claim 1, wherein the multicast receiver addressing is donevia the MAC layer.
 17. A computer-readable medium, comprising: code forcausing a computer to transmit a multicast frame associated with a firstmulticast receiver address; and code for causing a computer toretransmit a duplicate of the multicast frame, the duplicate beingassociated with a second multicast receiver address different from thefirst multicast receiver address, wherein the multicast receiveraddressing is done via the MAC layer.
 18. An integrated circuit,comprising: circuitry configured to: transmit a multicast frameassociated with a first multicast receiver address; and retransmit aduplicate of the multicast frame, the duplicate being associated with asecond multicast receiver address different from the first multicastreceiver address, wherein the multicast frame associated with the firstmulticast receiver address and the duplicate of the multicast frameassociated with a second multicast receiver address have a portion oftheir headers in common.
 19. An apparatus for reliable multicasting in awireless communication system, comprising: means for transmitting amulticast frame associated with a first multicast receiver address; andmeans for retransmitting a duplicate of the multicast frame, theduplicate being associated with a second multicast receiver addressdifferent from the first multicast receiver address.
 20. The apparatusof claim 19, further comprising: means for receiving a feedbackassociated with the multicast frame from at least one of a multicastgroup, wherein the received feedback determines the number of duplicateretransmissions of the multicast frame.
 21. The apparatus of claim 19,wherein the multicast frame associated with the first multicast receiveraddress and the duplicate of the multicast frame associated with asecond multicast receiver address have a portion of their headers incommon.
 22. The apparatus of claim 19, further comprising: means forsetting a threshold for a number of retransmissions for the multicastframe, wherein the means for retransmitting the duplicate of themulticast frame repeats until the threshold is met.
 23. An apparatus forreliable multicasting in a wireless communication system, comprising: aprocessor configured to transmit a multicast frame associated with afirst multicast receiver address and to retransmit a duplicate of themulticast frame, the duplicate being associated with a second multicastreceiver address different from the first multicast receiver, whereinthe multicast frame associated with the first multicast receiver addressand the duplicate of the multicast frame associated with a secondmulticast receiver address have a portion of their headers in common;and a memory associated with the processor.
 24. The apparatus of claim23, wherein the processor is further configured to receive a feedbackassociated with the multicast frame from at least one of a multicastgroup, wherein the received feedback determines the number of duplicateretransmissions of the multicast frame.
 25. The apparatus of claim 23,wherein the processor is further configured to set a threshold for anumber of retransmissions for the multicast frame, wherein theretransmitting the duplicate of the multicast frame repeats until thethreshold is met.